Hardfacing Material

ABSTRACT

The present invention discloses a kind of hardfacing alloy, which can be applied onto a workpiece&#39;s surface by any one surface treatment process in accordance with material, dimensions, and required properties of the workpiece. For example, this novel hardfacing material can be heated to a fully melted state or a partially melted state by using different types of heat sources, such that the melted hardfacing material can be coated onto the surface of any one workpiece to form a protective layer or a surface modification layer. As a result, the workpiece having the surface coating layer with superior characteristics exhibits outstanding functional performances and has a long service time.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to the technology field of alloymaterials, and more particularly to a hardfacing material.

2. Description of the Prior Art

Surface treatment or modification technologies are widely adopted forforming a coating layer onto the surface of a workpiece, so as to extendthe workpiece's service time. Hardfacing process is one kind of surfacemodification technology and used for coating a hardfacing material ontoa workpiece's surface by thermal spraying, meltallizing, build-upwelding, or sintering. After covering the surface of the workpiece bythe hardfacing material, mechanical characteristics like wearresistance, corrosion resistance and/or thermal resistance of theworkpiece's surface are then improved, such that service time of theworkpiece would be obviously extended.

Conventional hardfacing material is commonly a Fe-based, Co-based orNi-based alloy containing with other additional elements such as Cr, V,and/or Mo for enhancing corrosion resistance and thermal stabilitythereof. It is worth noting that, development and applications of thehardfacing alloy are found to be limited due to the fact that thecomposition design of the hardfacing alloy usually uses Fe, Co, or Ni asa principal element for forming the base alloy structure. As a result,workpieces coated with different surface modification layers made ofvarious conventional hardfacing materials are unable to satisfyrequirements of environments implemented with the workpieces. Forinstance, Ni-based and Co-based hardfacing alloys exhibit wearresistance and thermal stability superior than Fe-based hardfacingalloys, however, the Fe-based hardfacing alloys are low-cost surfacemodification materials having the outstanding mechanical strength.

From above descriptions, it is understood that the target applicationenvironments or workpieces of a hardfacing alloy should be firstlyconsidered when designing and developing the hardfacing alloy. Forexample, by selecting proper materials for forming a base alloystructure and simultaneously making the base alloy structure contain atleast one precipitation-strengthened alloy structure, a correspondinghardfacing material suitable for being processed to a surfacemodification layer on a specific workpiece is hence completed. Moreover,the specific workpiece having the particularly-developed surfacemodification layer is able to satisfy requirements of its applicationenvironment.

Differing from the fact that traditional or conventional alloys oftencontain one principal metal element, a new design concept ofhigh-entropy alloys (HEAs) has been disclosed by literature 1.Literature 1, written by Yeh et. al (hereinafter “Yeh”), is entitledwith “Nanostructured High-entropy Alloys with Multi-PrincipalElements—Novel Alloy Design Concepts and Outcomes” and published onADVANCED ENGINEERING MATERIALS 6(5)(2004), pp. 299-303). Particularly,Yeh defined that a high-entropy alloy must contain at least fiveprincipal elements with the concentration of each element being between35 and 5 at %. According to the definition of HEAs described inliterature 1, there are countless compositions for synthesizing HEAs.For instance, there are 1716 combinations of element from 5 elements to13 elements for constructing 1716 HEA systems when 13 elements arechosen. In each alloy system, different compositions with concentrationsin euiatomic or non-equiatomic ratio could be designed for synthesizingHEAs of the HEA system.

The so-called high entropy alloy (HEA) can benefit from the high entropystrengthening effects and show the advantages in lower density and lowercost of materials due to less refractory additions. In addition, theexperimental results have indicated that HESA possess goodmicrostructure stability, hot corrosion and oxidation resistance, aswell as high hardness, tensile and creep strength at elevatedtemperatures. Thus, based on literature 1's basic principle, inventorsof the present application have made great efforts to make inventiveresearch thereon and eventually provided a hardfacing material.

SUMMARY OF THE INVENTION

The primary objective of the present invention is to provide a kind ofhardfacing alloy, which can be applied onto a workpiece's surface by anyone surface treatment process in accordance with material, dimensions,and required properties of the workpiece. For example, this novelhardfacing material can be heated to a fully melted state or a partiallymelted state by using different types of heat sources, such that themelted hardfacing material can be coated onto the surface of any oneworkpiece to form a protective layer or a surface modification layer. Asa result, the workpiece having the surface coating layer with superiorcharacteristics exhibits outstanding functional performances and has along service time.

In order to achieve the primary objective of the present invention, theinventor of the present invention provides an embodiment for thehardfacing material, comprising:

-   -   at least four principal metal elements, being selected from the        group consisting of Al, Co, Cr, Cu, Fe, Mn, Mo, Ni, Nb, Ti, Ta,        V, W, and Zr, and a first summation mole number of the principal        metal elements is 50-90 percent of a total mole number of the        hardfacing material; and    -   at least one non-metal element, being selected from the group        consisting of B, C, N, O, and Si, and a second summation mole        number of the non-metal element is 5-50 percent of the total        mole number of the hardfacing material;    -   wherein two of the at least four principal metal elements are        selected from the group consisting of Al, Cr, Mo, Nb, Ti, Ta, V,        W, and Zr;    -   wherein each of the principal metal elements have a mole number        of principal metal element, and the mole number of principal        metal element is equal to or greater than 5 percent of the first        summation mole number.

In the embodiment of the hardfacing material, wherein the principalmetal elements and the at least one non-metal element form at least onebase alloy structure and at least one precipitation-strengthened alloystructure of the hardfacing material.

In the embodiment of the hardfacing material, wherein a product or asemi-product of the hardfacing material can be a powder, a wire, awelding rod, a cored wire, or a bulk.

In the embodiment of the hardfacing material, wherein the hardfacingmaterial is able to be coated on the surface of a target workpiece by asurface modification process selected from the group consisting of:meltallizing, build-up welding, thermal spraying, and sintering.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention as well as a preferred mode of use and advantages thereofwill be best understood by referring to the following detaileddescription of an illustrative embodiment in conjunction with theaccompanying drawings, wherein:

FIG. 1 shows an SEM image of a first best embodiment of a hardfacingmaterial according to the present invention;

FIG. 2 shows an SEM image of a second best embodiment of the hardfacingmaterial;

FIG. 3 shows an SEM image of a third best embodiment of the hardfacingmaterial; and

FIG. 4 shows an SEM image of a fourth best embodiment of the hardfacingmaterial.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

To more clearly describe a hardfacing material according to the presentinvention, embodiments of the present invention will be described indetail with reference to the attached drawings hereinafter.

Traditional hardfacing alloys often contain one kind of primaryelemental composition; for example, Fe-based, Co-based or Ni-basedhardfacing alloy containing with other additional elements such as Cr,V, and/or Mo for enhancing corrosion resistance and thermal stabilitythereof. Particularly, the present invention discloses a hardfacingmaterial comprises at least four principal metal elements at least fourprincipal metal elements and at least one non-metal element, wherein theprincipal metal elements and the at least one non-metal element form atleast one base alloy structure and at least oneprecipitation-strengthened alloy structure of the hardfacing material.It needs to further explain that, at least four principal metal elementsare selected from the group consisting of Al, Co, Cr, Cu, Fe, Mn, Mo,Ni, Nb, Ti, Ta, V, W, and Zr; more particularly, two of the at leastfour principal metal elements are selected from the group consisting ofAl, Cr, Mo, Nb, Ti, Ta, V, W, and Zr.

On the other hand, the at least one non-metal element, being selectedfrom the group consisting of B, C, N, O, and Si, and a second summationmole number of the non-metal element is 5-50 percent of the total molenumber of the hardfacing material. According to the present invention, afirst summation mole number of the principal metal elements is 50-90percent of a total mole number of the hardfacing material, and a secondsummation mole number of the non-metal element is 5-50 percent of thetotal mole number of the hardfacing material. Moreover, each of theprincipal metal elements have a mole number of principal metal element,and the mole number of principal metal element is equal to or greaterthan 5 percent of the first summation mole number.

Moreover, for proving the practicability of the hardfacing material ofthe present invention, inventors of the present invention have completeda variety of experiments.

First Experiment: Finding Out Proper Content of Elements forConstituting the Hardfacing Material

Following Table (1) and Table (2) record related data of the firstexperiment. From the two tables, it is found that Cr, Fe, Mn, and Ni areadopted for being as the principal metal elements contained by samplesof the hardfacing material, wherein the hardfacing material furthercomprises strengthening elements of Al and Mo for formingprecipitation-strengthened alloy structure of the hardfacing material.On the other hand, B and C are adopted for being as the non-metalelements in the samples. Based on the experimental data, it isunderstood that the hardness and the wear resistance of the samples 1-4increase with the growth of the non-metal element's content. It is worthnoting that, the growing content of the non-metal element's (i.e., theincreasing hardness of the hardfacing material) must causes thehardfacing material's tenacity decline. As a result, owing to lack oftenacity, the hardfacing material may be subject to cracks or break whenbeing implemented in an application environment. Therefore, based on thedata of the first experiment, the inventors have confirmed the elementsand content thereof for constituting the hardfacing material, which aresummarized as follows:

-   -   (1) a first summation mole number (FSMN) of the principal metal        elements (ME) is 64-85 percent of a total mole number of the        hardfacing material; and    -   (2) a second summation mole number (SSMN) of the non-metal        element (nME) is 15-36 percent of the total mole number of the        hardfacing material.

TABLE (1) ME1 ME2 ME3 ME4 ME5 ME6 nME Sample (at %) (at %) (at %) (at %)(at %) (at %) (at %) Hardness 1 Al Cr Fe Mn Ni Mo B HV521  2.9 24   38.39.6 5   1   19.2 2 Al Cr Fe Mn Ni Mo B HV1041 1.6 13.5 45.5 5.4 4.2 0.629.2 3 Al Cr Fe Mn Ni Mo B HV1258 1.5 12.9 43.3 5.2 4.1 0.5 32.5 4 Al CrFe Mn Ni Mo B HV1436 1.5 12.3 41.3 4.9 4.0 0.5 35.6 5 Al Cr Fe Mn Ni MoC HV841  3.4 46   17.2 11.5  5.7 1.1 14.9

TABLE (2) FSMN ME1 ME2 ME3 ME4 ME5 ME6 nME SSMN (%) (%) (%) (%) (%) (%)(%) (%) (%) 80.8 Al Cr Fe Mn Ni Mo B 19.2 3.59 29.7  47.4  11.88 6.191.24 19.2 70.8 Al Cr Fe Mn Ni Mo B 29.2 2.26 19.07 64.25  7.63 5.93 0.8529.2 67.5 Al Cr Fe Mn Ni Mo B 32.5 2.22 19.11 64.15 7.7 6.07 0.74 32.564.5 Al Cr Fe Mn Ni Mo B 35.5 2.33 19.0  64.0  7.6 6.2  0.78 35.5 84.9Al Cr Fe Mn Ni Mo C 14.9 4   54.18 20.26 13.55 6.71 1.3  14.9

From Table (2), it is also known that, each of the principal metalelements (Al, Cr, Fe, Mn, Mo, and Ni) have a mole number of principalmetal element, and the mole number of principal metal element is equalto or greater than 5 percent of the first summation mole number (FSMN).Moreover, engineers skilled in development and manufacture of hardfacingalloys must know that, target application environments or workpieces ofa specific hardfacing material should be firstly considered whendesigning and developing the hardfacing material. For example, byselecting proper materials for forming a base alloy structure andsimultaneously making the base alloy structure contain at least oneprecipitation-strengthened alloy structure, a corresponding hardfacingmaterial suitable for being processed to a surface modification layer ona specific workpiece is hence completed. Therefore, the specificworkpiece having the particularly-developed surface modification layeris able to satisfy requirements of its application environment. On theother hand, it needs to further explain that a product or a semi-productof the hardfacing material proposed by the present invention can be apowder, a wire, a welding rod, a cored wire, or a bulk. Moreover, thehardfacing material is able to be coated on a target workpiece's surfaceby any one type of surface modification process, such as meltallizing,build-up welding, thermal spraying, or sintering.

Second Experiment: Understanding the Characteristics of the HardfacingMaterials with Different Alloy Systems

Following Table (3) records related data of the second experiment. Fromthe Table (3), it is found that Al, Co, Cr, Cu, Fe, and Ni are adoptedfor being as the principal metal elements contained by samples 6-7 ofthe hardfacing material, wherein Al and Cr are elements belong toprecipitation-strengthened alloy structure of the hardfacing material.On the other hand, Co, Cr, Fe, Ni, and Ti are adopted for being as theprincipal metal elements (ME) contained by samples 8-9 of the hardfacingmaterial, wherein Cr and Ti are elements belong toprecipitation-strengthened alloy structure of the hardfacing material.Moreover, B and C are adopted for being as the non-metal elements (nME)in the four samples.

TABLE (3) ME1 ME2 ME3 ME4 ME5 ME6 nME Sample (at %) (at %) (at %) (at %)(at %) (at %) (at %) Hardness 6 Al Co Cr Cu Fe Ni B HV523  7.8 15.5 15.315.4 15.5 15.2 15.3 7 Al Co Cr Cu Fe Ni B HV774  6.7 13.3 13.5 13.2 13.313   27   8 Co Cr Fe Ni Ti C HV721 15.6 12.1 10.5 15.3 33.3 13.2 9 Co CrFe Ni Ti C  HV1015 13.5  9.7  8.8 13.4 29.7 24.9

Table (4) also records related data of the second experiment. From theTable (4), samples 10-11 of the hardfacing material contains elements ofAl, Cr, Ti, and Zr for forming precipitation-strengthened alloystructure of the hardfacing material. Moreover, B and Si are adopted forbeing as the non-metal elements in the two samples. On the other hand,samples 12-13 of the hardfacing material contains elements of Al, Cr,Ta, Ti, and Zr for forming precipitation-strengthened alloy structure ofthe hardfacing material. Moreover, O and N are adopted for being as thenon-metal elements in the two samples.

TABLE (4) ME1 ME2 ME3 ME4 ME5 ME6 nME nME (at %) (at %) (at %) (at %)(at %) (at %) (at %) (at %) Hardness 10 Al Cr Fe Ni Ti Zr B Si HV745 12.4 12.3 12.7 12.5 12.5 12.5 12.5 12.5 11 Al Cr Fe Ni Ti Zr B Si HV850 13.3 13.3 13.3 13.3 13.3 13.3  6.7 13.3 12 Al Cr Ta Ni Zr O HV1800 15.315.5 15.4 15.7 15.1 23   13 Al Cr Ta Ti Zr N HV1500 15.5 15.7 14.4 14.516.8 13.1 14 Al Cr Ta Ti Zr C N HV1500 12.2 14.2  8.9 10.8 10.3 15.827.8

The Best Alloy Systems for Fabricating the Hardfacing Materials

Following Table (5) and Table (6) list constituting elements and theiratomic percent for fabricating best embodiment(s) of the hardfacingmaterial proposed by the present invention.

TABLE (5) ME1 ME2 ME3 ME4 ME5 ME6 ME7 nME (at %) (at %) (at %) (at %)(at %) (at %) (at %) (at %) Hardness I Al Cr Mn Fe Ni Mo C HV785 3.446   11.5 17.6 5.7 1.1 14.7 II Al Cr Mn Fe Ni Mo B HV737 3.7 47.2 11.817.2 5.9 1.3 12.9 III Al Cr Mn Fe Ni Mo Nb C HV810 3.4 44.2 11.0 16.65.5 1.1 3.3 14.9 IV Al Cr Mn Fe Ni Mo Ti B HV765 3.1 41.7 10.4 15.6 5.21.0 6.3 16.7

TABLE (6) FSMN ME1 ME2 ME3 ME4 ME5 ME6 ME7 SSMN (%) (%) (%) (%) (%) (%)(%) (%) (%) 85.3 Al Cr Fe Mn Ni Mo C 3.99 53.93 20.63 13.48 6.68 1.2914.7 87.1 Al Cr Fe Mn Ni Mo B 4.25 54.19 19.35 13.55 6.77 1.49 12.9 85.1Al Cr Fe Mn Ni Mo Nb C 4.0  51.94 19.51 12.93 6.46 1.29 3.88 14.9 83.3Al Cr Fe Mn Ni Mo Nb B 3.72 50.06 18.73 12.48 6.24 1.20 6.3  16.7

FIG. 1-FIG. 4 show SEM images of a first best embodiment, a second bestembodiment, a third best embodiment, and a fourth best embodiment of thehardfacing material, respectively. Information of symbols I, II, III,and IV are provided in following Table (7).

TABLE (7) I II III IV V Light-gray Deep-gray Deep colour White Blackcarbide base phase base phase carbide carbide (or boride) structurestructure (or boride)

From the provided SEM images, it is found that each of the bestembodiments of the hardfacing material comprise at least one base phasestructure and at least two compound phase structures, wherein thecompound phase is regarded as precipitation-strengthened alloy structureof the hardfacing material. Therefore, the hardfacing material of thepresent invention can be coated on a target workpiece's surface, so asto enhance mechanical characteristics of the workpiece such as wearresistance, corrosion resistance and/or thermal resistance. it needs tofurther explain that a product or a semi-product of the hardfacingmaterial proposed by the present invention can be a powder, a wire, awelding rod, a cored wire, or a bulk. Moreover, the hardfacing materialis able to be coated on a target workpiece's surface by any one type ofsurface modification process, such as meltallizing, build-up welding,thermal spraying, or sintering.

For instance, it is able to dispose powdered hardfacing material ontothe target workpiece's surface, and then transmit the workpiece into aheating furnace, such that a protect layer made of the hardfacingmaterial is formed on the workpiece's surface through sintering process.

Therefore, through above descriptions, the hardfacing material of thepresent invention have been introduced completely and clearly; insummary, the present invention includes the advantages of:

(1) The present invention discloses a kind of hardfacing alloy, whichcan be applied onto a workpiece's surface by any one surface treatmentprocess in accordance with material, dimensions, and required propertiesof the workpiece. For example, this novel hardfacing material can beheated to a fully melted state or a partially melted state by usingdifferent types of heat sources, such that the melted hardfacingmaterial can be coated onto the surface of any one workpiece to form aprotective layer or a surface modification layer. As a result, theworkpiece having the surface coating layer with superior characteristicsexhibits outstanding functional performances and has a long servicetime.

The above description is made on embodiments of the present invention.However, the embodiments are not intended to limit scope of the presentinvention, and all equivalent implementations or alterations within thespirit of the present invention still fall within the scope of thepresent invention.

What is claimed is:
 1. A hardfacing material, comprising: at least fourprincipal metal elements, being selected from the group consisting ofAl, Co, Cr, Cu, Fe, Mn, Mo, Ni, Nb, Ti, Ta, V, W, and Zr, and a firstsummation mole number of the principal metal elements is 50-90 percentof a total mole number of the hardfacing material; and at least onenon-metal element, being selected from the group consisting of B, C, N,O, and Si, and a second summation mole number of the non-metal elementis 5-50 percent of the total mole number of the hardfacing material;wherein two of the at least four principal metal elements are selectedfrom the group consisting of Al, Cr, Mo, Nb, Ti, Ta, V, W, and Zr;wherein each of the principal metal elements have a mole number ofprincipal metal element, and the mole number of principal metal elementis equal to or greater than 5 percent of the first summation molenumber.
 2. The hardfacing material of claim 1, wherein the principalmetal elements and the at least one non-metal element form at least onebase alloy structure and at least one precipitation-strengthened alloystructure of the hardfacing material.
 3. The hardfacing material ofclaim 1, wherein a product or a semi-product of the hardfacing materialcan be a powder, a wire, a welding rod, a cored wire, or a bulk.
 4. Thehardfacing material of claim 1, being able to be coated on the surfaceof a target workpiece by a surface modification process selected fromthe group consisting of: meltallizing, build-up welding, thermalspraying, and sintering.